Cone type well drill



Dec. 18, 1956 E. A. MORLAN 2,774,571

CONE TYPE WELL DRILL Filed July 6, 1954 fr W//7 A. Mar/ah INVENTOR.

A TTOR/VEY United States Patent CONE TYPE WELL DRILL Erwin A. Morlan,Houston, Tex., assignor to Hughes Tool Company, Houston, Tex., acorporation of Delaware Application July 6, 1954, Serial No. 441,360

4 Claims. (Cl. 255-347 This invention relates to well drills of the conetype in which the cutters, mounted upon inwardly extending shafts, aresubstantially conical in shape. More particularly the invention isconcerned with well drills, of the type indicated, capable ofeffectively drilling hard abrasive formations.

This general type of bit is Well known in the art, the inventionresiding in the particular cutting structure provided upon the cuttercones.

The invention relates to and broadly comprehends that disclosed andclaimed in copending application No. 257,314, filed November 20, 1951,Patent No. 2,687,875, issued August 3, 1954, for well drills andcomprehends an improvement over the specific structure shown therein asan illustrative embodiment of that invention.

Difiiculty has been experienced in obtaining rock bits that willeffectively drill at a satisfactory rate and desired footage in earthformations which have high compressive strength, which are extremelyhard and which at the same time are excessively abrasive. To overcomethis difliculty it has been proposed, as disclosed in said copendingapplication, to provide a rolling cutter type of earth boring drill inwhich the rolling cutters are provided with series of wear resistantinserts secured in and protruding from the cutting surfaces of thecutter bodies, the protruding portion of the inserts being rounded orovoid so that each insert presents an arcuate surface for engagementwith and disintegration of the material to be removed by the cutters.

In a preferred form such a rock bit has heretofore been provided withthree conical cutters, one of such cutters having a spearpoint orcutting extension at its smaller end. Such spearpoint extends across thebit axis whereby it functions to disintegrate the earth formation at andnear the axis of the bit. The other cutters terminate outwardly from theaxis of the bit so that there will be no interference among the cutters.

In the drilling of some extremely abrasive earth formations such as thebromides, taconite and quartzitic formations other than chert it hasbeen found that destruction of the spear-point on the one cutter isextremely rapid and that such destruction renders the bit unfit forfurther use even though the remaining cutter structure of the cutters isin such condition that considerable useful life remains.

An object of the present invention is to provide an improved well drillwhich is so constructed that maximum benefit is had from all parts ofthe cutting structure.

Another objective is to provide a drill bit having conical cutters, eachcutter having a nose cutting structure extending substantially to thebit axis whereby the cutters cooperate to effect disintegration of theearth formation proximate the axis of the bore hole being formed by thebit.

Still another object is to provide an earth boring drill in which thecutters have nose cutting structures in confronting relation proximatethe axis of the bit together with cutting structure outwardly thereofwhich are so constructed and arranged as to cooperate in disintegratingthe entire bottom of the hole being drilled.

A still further object is to provide a cone type of well drill in whichthe confronting cone noses are provided with Wear resistant insertshaving rounded or ovoid protrusions at the surfaces of the cutterbodies, such protrusions acting as cutting elements to disintegrate theearth formation at and proximate the bit axis.

Another and more specific object is to provide, in the preferred form ofthe invention as herein disclosed, a cone type of well drill in whichthe conical cutters have confronting cone noses provided with cuttingelements which operate in a noninterfering manner to cut the earthformation at and near the axis of the bore being drilled, the conicalcutters having additional cutting elements outwardly from the cone nosesin interfitting relation to cut the outer portion of the bottom and toprovide a self-cleaning action in the drill.

The foregoing objects together with other objects and advantages of theinvention will be more fully apparent from the following descriptionconsidered in connection with the accompanying drawings in which:

Fig. 1 is an elevational view of a well drill or bit embodying theinvention, the view being taken generally on line 1-1 in Fig. 2, aportion of the bit being shown in elevation and a portion being shown insection and rotated into the plane of the paper to better illustrate theconstruction and relationship of components of the drill; 1

Fig. 2 is a bottom view of the well drill.

Fig. 3 is a composite view showing in superposed relationship thecutting elements of the cutters of a well drill embodying the inventionas they move across a selected radial plane of a well bore beingdrilled.

Fig. 4 is an enlarged, fragmentary, bottom view of the well drillillustrating the insert arrangement on the nose portions of the conicalcutters.

An embodiment of the invention is shown in the drawings as comprising athree-cone drill bit which comprises a head 21 having three downwardlyextending legs arranged symmetrically about the axis of the bit of whichtwo are shown at 22. Each leg has an inwardly and downwardly extendingshaft 23 having its inner end enclosed by a cutter shown generally at24. Each cutter 24 is rotatably mounted upon its shaft by a suitablebearing structure which may assume any of various forms well known inthe art and which is shown generally in the drawings as a combination ofantifriction and friction bearing elements.

Each of the cutters 24 comprises a body 25 as best seen in Fig. 1, thecutting elements associated with the cutter body including series ofwear resistant inserts 26- secured in the body and protruding from thesurface thereof, the protruding portion of the inserts being rounded, orovoid, whereby such cutting elements function throughout the life of thebit to disintegrate the bottom of the hole being drilled. These insertsare preferably a sintered carbide and, more specifically it has beenfound advantageous to use sintered tungsten carbide although it is to beunderstood that other metal carbides such as chromium, molybdenum,tantalum or mixed carbides may be used. Alsothe inserts are preferablysecured in place in the cutter body by being forced into openings orsockets which are slightly smaller than the outer diameter of theinserts, the interference fit causing an expansible force to be exertedupon the metal surrounding each insert as it is forced into position.This method of installation of an insert provides a high holding powerupon the inserts such holding power being accentuated by the fact thatthe wall of'the opening-or socket becomes conjugate with the peripheryof the insert as it is forced into terminal position. It

is to be understood that this preferred manner of installing the insertsis presented as illustrative only and not by way of limitation of theinvention.

The three cutters of the well drill must cut the entire bottom of thehole being drilled but at the same time must present a limited number ofcutting elements upon bottom at a given instant else excessive weight isnecessary in order to effect desired cutting action of the bit.Accordingly the three cutters 24 are not identical and are respectivelyfurther identified by the numeral 27, 2i; and 29.

Each cutter has a gage cutting portion 310 (Fig. 1) which includes anannular series of wear resistant inserts 31, this portion of the cuttersserving to maintain uniform gage of the hole being drilled. Each cutteralso has a bottom cutting portion generally indicated at 32. Thisportion comprises the nose 33 and, outwardly therefrom, series ofcutting elements shown in spaced annular rows. Preferably these seriesof cutting elements are located in spaced annular lands shown at 34 and35 on cone 2'7, at 36 and 37 on cone 28 and at 38 and 39 on cone 29.These lands are so located on the respective cutter bodies that theprotruding ends of the series of inserts in each land overlies orextends slightly into a groove between lands in the adjacent cutters. Inother words, intervening grooves and the protruding portions of theinserts are so oriented that there is an interfitting relationship amongthe rows of these cutting elements of the cutters outwardly from theaxis of the drill. This provides a self-cleaning action of the cuttersbut equally important, it enables utilization of limited space availablewhereby a maximum of thickness of the cutter body 25 is had toeffectively hold the cutter elements 26, and in providing in the cutterstructure adequate strength to withstand the severe stresses to which itis subjected in normal use.

The noses 33 of the cutters 27, 28 and 29 are specially designed tocarry a sufficient number of the cutter elements 26 and so arranged asto cooperatively disintegrate bottom at and near the axis of the borebeing drilled. At the same time there must be no interference betweencutters. To this end the surface of each nose 33 lies on a slightlysmaller cone than that defined by the surfaces of the lands on thecutter body. Thus the ovoid protruding portion of the wear resistantinserts in the noses are in close confronting relation but are free frominterference. Such inserts are also so oriented on the respective nosesthat their tracks on bottom are such as to provide desireddisintegrating action at this point.

Preferably, as shown, the nose inserts are also arranged in annularseries and these series are spaced sequentially outwardly from the axisof rotation of the bit. This is best illustrated by reference to Figs.2, 4, and 3 of which the latter shows a section through one-half of anearth bore being drilled by a bit embodying the invention. The bottom ofthe bore is shown at 40 and the side wall thereof is shown at 41. Therespective series of cutting elements will, through successiverevolutions of the bit, engage the bottom of the bore hole in therelative positions shown radially of the bore hole in Fig. 3.

For example, the element 1 in the extreme nose of the cutter 29 isclosest the axis of the bore hole. This cutter element together with theinserts proximate the inner end of the adjacent noses will cut so nearthe axis of the bit that the earth formation will be disintegrated toand adjacent the axis. Next adjacent the element 1 is series 2 on cone27. The series outwardly on succeeding cones are shown at 3 to 19inclusive.

It is to be noted that the series i7, 18 and 19 are arrangedsubstantially in a single annular path at the juncture of the bottom 46and the side wall 41 of the well bore. This feature of construction isintended to operate effectively at this point where there is arelatively large volume of formation material to be removed and whereconditions are particularly severe because the bottom and side walls aremutually self-supporting. This feature also facilitates cutting to gagewhereby the gage cutting elements 31 are capable of maintaining accurategage throughout the life of the bit.

The traction which determines the rate of rotation of the respectivecones 27, 28 and 29 is furnished by the cutting elements outwardly fromthe noses 33. Hence, this portion of the bottom cutting portion 32possesses a true rolling action. That is to say, there is little, ifany, slip or tearing action due to movement of a cutting elementrelative to the bottom as the element is in engagement with bottom.Since the wear resistant inserts in the noses 33 protrude from a conicalsurface which is slightly smaller than that defined by the landsoutwardly therefrom, there is a slight differential movement betweeneach of these inserts and the bottom of the hole as each such insertmoves into engagement with bottom and then withdraws from suchengagement. This provides a desirable disintegrating action at thispoint but at the same time produces a destructive action upon the noseinserts. This destructive action is offset by the concentration of thenose inserts proximate the axis of the bore and hence the objectives ofthe invention are attained by the structure described as a preferredembodiment of the invention.

Broadly the invention comprehends a new and improved cone type welldrill capable of eifectively cutting hard and abrasive formations, thecutting elements on the respective cutters being so arranged that amaximum rate of drilling and footage may be had.

The invention claimed is:

1. An earth boring drill comprising, a head, a plurality of conicalcutters rotatably mounted thereon, each of said cutters comprising abody having a nose portion terminating proximate the axis of the drill,each of said nose portions having cutter elements thereon comprising aplurality of wear resistant inserts secured therein and each having anovoid protrusion at the surface thereof, said inserts on the respectivenose portions being in confronting and noninterfitting relation andbeing arranged thereon to engage and produce overlapping tracks upon thebottom of the bore being drilled and to thereby disintegrate the earthformation at and proximate the axis of the drill, said cutter bodiesincluding spaced annular lands outwardly of said nose portions, saidlands being spaced on the bodies so that each land overlies the spacebetween lands on the adjacent cutters, and a series of wear resistantinserts secured in each of said lands, said inserts having ovoidprotrusions at the surface of the lands, whereby said protrusions formcutting elements in interfitting relationship to effect a self-cleaningaction and to disintegrate bottom outwardly of said nose portions.

2. An earth boring drill comprising, a head, a plurality of conicalcutters rotatably mounted thereon, each of said cutters comprising abody having a nose portion terminating proximate the axis of the drill,each of said nose portions having a plurality of annular series ofcutter elements thereon, each of said series comprising a plurality ofwear resistant inserts secured therein and each having an ovoidprotrusion at the surface thereof, said inserts on the respective noseportions being in confronting and noninterfitting relation and beingarranged to engage the earth formation and produce overlapping tracksthereon and to thereby disintegrate the earth formation traversed by thenose portions, spaced annular lands on said cutter bodies outwardly fromsaid nose portions, said lands being spaced on the cutter bodies torespectively overlie the space between the lands on the adjacentcutters, and a series of Wear resistant inserts secured in each of saidlands and having their outer ends protruding from the surfaces of thelands and in interfitting relationship with series of inserts in theadjacent cutters.

3. An earth boring drill comprising, a head, a plurality of conicalcutters rotatably mounted thereon, each of said cutters comprising abody having a nose portion terminating proximate the axis of the drill,a plurality of axially spaced annular series of Wear resistant insertson each nose, each of said inserts protruding from the surface of theassociated nose, corresponding series of inserts on the respective nosesbeing so axially spaced along the noses that a track made by one seriesoverlaps the track made by the corresponding series on another nose, andadditional axially spaced annular series of inserts secured in eachcutter outwardly from the nose portion to the base of the cutter, saidadditional series being so axially spaced along the cutters that thetracks rnade thereby are in concentric closely spaced relation and thebottom outwardly from the nose portions is disintegrated thereby.

4. In an earth boring drill having a plurality of conical cuttersrotatably mounted thereon, each of said cutters having annular series ofWear resistant inserts arranged thereon and protruding from the surfacethereof to disintegrate the entire bottom of the hole being formed bythe drill; the improvement comprising nose portions on the cutters inmutually confronting relation and terminating proximate the axis of thedrill, a plurality of axially spaced annular series of wear resistantinserts secured in each nose and protruding from the surface thereof,series of inserts on the respective noses being so spaced along thenoses that a track made by one series overlaps the track made by thecorresponding series of another nose whereby the nose portionsdisintegrate the formation traversed by said nose portions.

References Cited in the file of this patent UNITED STATES PATENTS2,117,679 Reed May 17, 1938 2,318,370 Burch May 4, 1943 2,626,128 BoiceJan. 20, 1953 2,687,875 Morlan et a1. Aug. 31, 1954

